Recently, liquid crystal displays, for example, are widely used in liquid crystal televisions, monitors, portable telephones and the like as flat panel displays that are thinner and lighter than conventional cathode ray tube devices. Such liquid crystal display devices have a lighting device (backlight) that emits light, and a liquid crystal panel, which has a plurality of pixels, that displays desired images by acting as a shutter of light emitted from a light source provided in the lighting device. A display signal generator is used in this type of liquid crystal display device to generate display signals for performing image display using input image signals for reference, and to output the display signals as instruction signals for the lighting device (light source) and the liquid crystal panel (pixel array unit). As a result, the input images corresponding to the input image signals are displayed on the liquid crystal display device.
The abovementioned liquid crystal display device includes a drive system that divides one frame into three sub-frame phases by using light-emitting diodes (LED) of the three colors of red (R), green (G) and blue (B) as light sources and sequentially flashing LEDs of the three colors, displays red only images, green only images, and blue only images in order in three continuous sub-frame phases, and reproduces the display colors of the input images in each pixel by superposing the sub-frame phases in the temporal direction in a liquid crystal panel not provided with a color filter. This drive system, which is also called a field sequential drive system, is known in the related art.
There is a problem in the liquid crystal display device of the field sequential system in that, since the response speed of liquid crystal is slow, an accurate display intensity in the sub-frame phase for each color cannot be achieved and the display color of the image represented by superposing the sub-frame phases is quite different from the input image.
To solve this problem, a method has been proposed, as disclosed in for example the below mentioned patent document 1, to refer to the immediately preceding color sub-frame phase signals to correct the subsequent color sub-frame phase signals. Specifically, in the conventional display signal generator and image display method, in each of the abovementioned sub-frame phases, the response inadequacy of the liquid crystal panel is compensated by generating and outputting an instruction signal to the liquid crystal panel so that a voltage that corresponds to an emphasized gradation signal and that is larger or smaller than a pixel gradation signal corresponding to the input image signal is supplied to the pixel, and a reduction in pixel color purity caused by the response characteristics is compensated to allow for improved image quality in the liquid crystal display device.